This invention relates to catalytic compositions and their use, especially for the conversion of hydrocarbonaceous feedstocks. In particular, the invention involves the use of catalysts having a shape which provides great flexibility for a variety of applications.
A number of catalyst shapes have been described in the prior art. U.S. Pat. No. 2,408,164 to Foster discloses catalyst shapes including solid and hollow cylinders, elongated star shapes, cylinders with corrugated edges, etc. Similar shapes are also shown in U.S. Pat. No. 3,997,426 to Montagna et al. U.S. Pat. No. 3,966,644 and U.S. Pat. No. Re. 30,155 issued to Gustafson disclose trilobal catalysts for hydrocarbon conversion. U.S. Pat. Nos. 3,674,680 and 3,764,565 to Hoekstra and Jacobs disclose catalyst shapes designed to eliminate catalytic material more than 0.0015 inches from the catalyst surface. U.S. Pat. No. 3,347,798 to Baer et al. discloses the production of hollow bead catalysts. U.S. Pat. No. 3,957,627 discloses spherical catalysts having a void center and a hole extending to the external surface. U.S. Pat. Nos. 4,116,819 and 4,133,777 disclose catalysts in the shape of elongated extrudates having alternating longitudinal grooves and protrusions on the surface.
The purpose of providing shaped catalyst particles has generally been to increase the surface area/volume ratios over conventional shapes such as cylinders, spheres, etc. While the surface area/volume ratio can be increased merely by reducing the size of catalyst particles, reductions in size generally result in larger pressure drops and smaller void sizes in fixed catalyst beds. A difficulty encountered in many prior art shaped catalysts is that the shapes permit the particles to interlock. Interlocking can occur whenever protrusions of the shaped catalyst are sized so that they can easily enter the recesses of adjacent catalyst particles. Interlocking of catalyst particles reduces the void fraction of the catalyst bed, decreases the effective surface area of the catalyst bed, and can increase the pressure drop across the bed.